mRNA uridylation as a novel post-transcriptional process regulating seed maturation – SeedUTail

Seeds are of crucial biological and economic importance. Seed agronomic traits, such as seed vigor and nutritional value, are established during seed development under the control of complex and multi-layer processes, including post-transcriptional regulation. The SeedUTail project tackles the importance of mRNA uridylation in the post-transcriptional regulation of developing seeds, a previously unexplored aspect of mRNA metabolism in seeds. In the last decade, mRNA uridylation, i.e uridine addition at 3’ end of mRNA, has emerged as a prevalent modification with an important function in post-transcriptional regulation. mRNA uridylation is a highly conserved mechanism in most eukaryotes, from fission yeast to plants and humans, and represents an integral step of mRNA degradation pathways. In Arabidopsis, we showed that mRNA uridylation prevents the accumulation of excessively deadenylated mRNA, possibly by both favoring their 5’ to 3’ degradation and hindering deadenylation. This function is important to avoid the biogenesis of illegitimate siRNAs that silence endogenous mRNAs and strongly impact plant growth and development.
The global objective of the SeedUtail project is to study molecular mechanisms of mRNA uridylation in the specific context of seed development and to evaluate its importance for seed physiology. Using high-throughput approaches based on Oxford Nanopore or Illumina sequencing technologies, we will identify all mRNA targets of uridylation and monitor the dynamic of uridylation throughout seed development. The main proteins involved in seed mRNA uridylation will be characterized and their impact will be evaluated on mRNA metabolism, hormonal metabolism and agronomical traits of seeds. The most important part of the project will be performed in the model plant Arabidopsis, for which numerous genetic tools are available, including a collection of mutants impaired in mRNA uridylation and degradation. Yet, we will tackle the diversity of mRNA uridylation patterns in seeds across angiosperms by analysis mRNA uridylation in seeds of species representative of monocots and dicots. The SeedUtail project participates to a better understanding of a new post-transcriptional process regulating a key developmental transition in plants. Beyond its fundamental scientific interest, this project could help in a middle term to develop strategies to improve agronomical traits, such seed germination or longevity.